In some locations, it may be important to monitor the concentration of H2S (hydrogen sulfide) to alert people of hazardous levels of the gas. Various H2S monitors are available for that purpose. Examples of such monitors and related systems are disclosed in U.S. Pat. RE40,238; U.S. Pat. Nos. 6,954,143 and 7,463,160; all of which are specifically incorporated by reference herein.